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Vcore Fluctuation under load

Last response: in Overclocking
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January 26, 2007 3:29:21 AM

Hey all,

I am using an E6600 on a Asus P5B Deluxe Wifi and just got it run completely stable at 3.5 Ghz. However, in the bios my vcore is set to 1.4125v, but using speedfan it says its at 1.37v. Right now, I am trusting speedfan unless someone think speedfan is giving the wrong reading...
Anyways, whenever I run dual instances of prime95, according to speedfan, the voltage drops to 1.34v and stays stable with +- .01v as long as prime95 is running. As soon as I stop both instances, the vcore returns to 1.37v.
Anyone know if this is normal and why that's happening?
Thanks!

EDIT:

Intel E6600 @ 3.5Ghz
Asus P5B Dlx wifi
Vcore idle: 1.368v
Vcore on full load: 1.34v
2 sticks of 1gb ram of OCZ XTC Platinum @ default settings for now
Western Digital Raptor 76Gb
Seagate 500 GB
ATI x300 (placeholder for now)
750W Silverstone PSU

More about : vcore fluctuation load

January 26, 2007 7:48:49 PM

anyone know? I don't like bumping my own posts but I am really curious to know why the processor is doing this :) 
January 26, 2007 8:53:48 PM

What PSU??? If it is not good name/rated high enough, that will be your problem. What video card? You should post complete spec, we're not mind readers!
Mike.
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January 26, 2007 10:43:46 PM

i got a 750W Silverstone PSU with a ATI X300 SE, so I doubt it's the PSU.
I am running:

Intel E6600 @ 3.5Ghz
Asus P5B Dlx wifi
Vcore idle: 1.368v
Vcore on full load: 1.34v
2 sticks of 1gb ram of OCZ XTC Platinum @ default settings for now
Western Digital Raptor 76Gb
Seagate 500 GB
ATI x300 (placeholder for now)
January 26, 2007 11:24:26 PM

Don't stress. Fluctuations are perfectly normal and is due to the mobo. My even fluctuates between 1.24 and 1.21 and is rock solid rendering at full load 24/7.
January 27, 2007 6:00:55 PM

Yes this is a normal phenomena on P5B mobother boards, vcore varies according to cpu needs under different loads.

Warwickmike
January 27, 2007 7:04:38 PM

This is a common occurrence among asus if not most motherboards.

There nothign wrong with your PSU as long as you didnt go for the cheap one and have some decent wattage, I believe 450-500W is pretty much what anyone needs unless you are running some superhero of a video card.

The problem lies in how you motherboard creates the Vcore.
Crash course: The capacitors and inductors (toroids) around and tot he side of you cpu slot, or even off on thier own daughter card in some cases create a DC-DC converter. What happens is the incoming power from your atx connector is fed thru a high frequency generator (dont believe me? stick an oscilloscope probe the the + side of an empty capacitor pad near the power converter, typically in the left corner of the board and 3/8" in diameter) and using the wonderful properties of inductance, resistance, and capacitance (aka LRC) they get the desired voltage out

Don't kid yourself, a large Vcore swing can have consequences. For example, you get some mild tests done and find outwhat the proc needs to just survive so you increase the level of testing and find you need to up the voltage again, and again and again... now finally to achieve stable OC you are settign the system to say .25 to as much as .50 V higher than that first mild OC. Now you take off the load and the voltage surges. Now providing that you didnt set it so high that the overvoltage protection on the board didnt trip you now have the processor sitting idle with a hellacious amount of voltage running thru it. This is NOT good as you are essentially cooking that processor. Now more voltage means more cooling and i agree, you have to cool an OC'ed proc more then a standard becasue it is generating a LOT more heat. The fact is, with all OCing, you ARE killing the proc, your operating it outside of its designed limits, its a fact of life, you gotta deal with it just like the rest of us.

So what are you to do? Well this is the fun part. The board i am basing this off of is an asus p4p800-e deluxe and an asrock dual sata 2, and i imagine most all motherboards would be fixed in a similar manner as they all use the some power conversion technology.

Controlling the cpu power supply is an amplifier which looks at the voltage, computes an error function and adjusts the power accordingly. IF you modify the way it handles its job, you can reduce that Vcore swing also known as Vdroop. There are several ways of handling this, just search google for "p4p800 Vdroop mod". Yes they all involve soldering.

Don't know how to solder? Shame on you, its a useful skill to be able to fix most small electiral issues as well as make something really do your bidding.

In short, either you "fix" it or find a buddy who can fix it, the benefit of tightening up that Vdroop is that you typically dont have to run as many volts to get your oc stable, my prescott needed .3 volts less after doing it, i unfortunately dont remember what the end voltage was though.

Worried about voiding the warranty by adding/modifying components on the MB? Don't worry about it, you already voided it by OC'ing :D 
January 28, 2007 6:11:32 PM

thanks a lot for the replies! ill take a look into vdroop mods
January 30, 2007 2:47:53 AM

Quote:
Hey all,

I am using an E6600 on a Asus P5B Deluxe Wifi and just got it run completely stable at 3.5 Ghz. However, in the bios my vcore is set to 1.4125v, but using speedfan it says its at 1.37v. Right now, I am trusting speedfan unless someone think speedfan is giving the wrong reading...
Anyways, whenever I run dual instances of prime95, according to speedfan, the voltage drops to 1.34v and stays stable with +- .01v as long as prime95 is running. As soon as I stop both instances, the vcore returns to 1.37v.
Anyone know if this is normal and why that's happening?
Thanks!

EDIT:

Intel E6600 @ 3.5Ghz
Asus P5B Dlx wifi
Vcore idle: 1.368v
Vcore on full load: 1.34v
2 sticks of 1gb ram of OCZ XTC Platinum @ default settings for now
Western Digital Raptor 76Gb
Seagate 500 GB
ATI x300 (placeholder for now)
750W Silverstone PSU

Most MB's, virtually all, will have the VCore dropping a little when CPU under load.

No voltage regulator I have come across will maintain perfect ie. exact same volts at no load and at full load.

A little VCore drop is OK.

If your worried about it, you could just increase the Vcore very slightly under no load :idea: so that when it is under full load, the voltage will be at the level you want.
!